Mobile communications network, infrastructure equipment, communications device and methods

ABSTRACT

A communications device for use in a mobile communications network, the mobile communications network comprising one or more other infrastructure equipment, the infrastructure equipment and other infrastructure equipment each providing wireless connectivity within at least one cell, wherein the communications device includes transmitter circuitry configured to transmit signals to the infrastructure equipment, receiver circuitry configured to receive signals from the infrastructure equipment, and controller circuitry configured to control the transmitter circuitry and the receiver circuitry. The controller circuitry controls the transmitter circuitry and the receiver circuitry to communicate wirelessly with at least a first of the infrastructure equipment including by the use of a radio bearer, to receive a reconfiguration message from the first infrastructure equipment to effect re-establishment of its radio link control protocol layer, and subsequently to re-establish its radio link control protocol layer in response to the reconfiguration message.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/608,199, filed Oct. 25, 2019, which is based on PCT filingPCT/EP2018/055800, filed Mar. 8, 2018, which claims priority to EP17168565.4, filed Apr. 27, 2017, the entire contents of each areincorporated herein by reference.

BACKGROUND Field

The present disclosure relates to apparatus and methods for handlingradio bearers in a telecommunications network.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Mobile telecommunications systems, such as those based on the 3GPPdefined UMTS and Long Term Evolution (LTE) and Long Term EvolutionAdvance (LTE-A) architectures, are applicable to communications betweennetworked user devices such as mobile telephones, and more widely alsoto applications such as the Internet of Things. The networked devicesare supported by a telecommunications network comprising base stationsof various configurations offering connection coverage over particularareas, known as cells, and the base stations are in turn supported by acore network. Transmission of data and other signalling between thesevarious entities is achieved by the use of radio bearers which transportthe required messages, for example as a signalling radio bearer whichcarries operational information for the entities, or a data radio bearerwhich carries data. In some instances a bearer is direct between twoentities (a base station and a user device), one sending the message andthe other receiving it. In other cases, a radio bearer configured indual connectivity (where a user device can connect to both a master anda secondary base station) may be used, allowing a received message to bedivided between the radio handling resources of two receiving entities.This radio bearer configured in dual connectivity may be, for example, asplit bearer. Hence, a radio bearer is divided between two basestations, each of which passes its part of the bearer to a user device.The user device is appropriately configured with resources to handledata received from each base station so that it can manage the bearer.This arrangement shares resources and enhances speed and efficiency.

The splitting of bearers in this way requires consideration of theoperation of the resources in both of the entities between which thebearer is split, and the resources in the user device corresponding toeach entity. Resources for each side of the bearer should be maintainedin an operational state for successful handling of the message.

SUMMARY

The present disclosure can help address or mitigate at least some of theissues discussed above.

Respective aspects and features of the present disclosure are defined inthe appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the present technology. The described embodiments,together with further advantages, will be best understood by referenceto the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 shows a schematic representation of an example mobiletelecommunications network or system;

FIG. 1A shows a schematic representation of an example user equipmentfor use in a network such as the FIG. 1 example;

FIG. 1B shows a schematic representation of an example base station foruse in a network such as the FIG. 1 example;

FIG. 2 shows a schematic representation of base stations and userequipment arranged for dual connectivity;

FIG. 3 shows a schematic representation of base stations and userequipment with cells arranged in groups;

FIG. 4 shows a schematic representation of an example user planeprotocol stack for dual connectivity;

FIG. 5 shows a schematic representation of a modified example user planeprotocol stack for dual connectivity;

FIG. 6 shows a ladder diagram of steps in a reconfiguration (“change”)procedure for use following a protocol counter rollover in a secondarycell group within a network;

FIG. 7 shows a ladder diagram of steps in an example procedure for usefollowing a protocol counter rollover in a secondary cell group within anetwork;

FIG. 8 shows a first example signal flow diagram between a transmittingentity and a receiving entity where multiple PDUs may be received withthe same sequence number;

FIG. 9 shows a second example signal flow diagram between a transmittingentity and a receiving entity where multiple PDUs may be received withthe same sequence number in accordance with embodiments of the presenttechnique; and

FIG. 10 shows a schematic representation of how a receiving RLC entitymay differentiate between and discard one of two received PDUs with thesame sequence number in accordance with embodiments of the presenttechnique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a schematic diagram illustrating some basic functionalityof a mobile (cellular, wireless) telecommunications network/system, inthis example operating generally in accordance with LTE principles, andwhich may be adapted to implement embodiments of the disclosure asdescribed further below. Various embodiments of FIG. 1 and theirrespective modes of operation are well-known and defined in the relevantstandards administered by the 3GPP (RTM) body, and also described inmany books on the subject, for example Holma and Toskala [1]. It will beappreciated that operational aspects of the telecommunications networkwhich are not specifically described below may be implemented inaccordance with any known techniques, for example according to therelevant standards and known variations thereof. Furthermore, it will beappreciated that whilst some specific examples described herein mayrefer to implementations based around particular 3GPP implementations,the same principles can be applied regardless of the underlyingoperating principles of the network. That is to say, the same principlescan be applied for wireless telecommunications networks operating inaccordance with other standards, whether past, current or yet to bespecified.

The network 100 in FIG. 1 includes a plurality of base stations 101connected to a core network 102. Each base station provides a coveragearea or cell 103 within which data can be communicated to and fromterminal devices or user equipment 104 within the respective coverageareas 103 via a radio downlink DL. Data is transmitted from userequipment 104 to the base stations 101 via a radio uplink UL. The uplinkand downlink communications are made using radio resources that may beused by the operator of the network. The core network 102 routes data toand from each user equipment 104 via the respective base stations 101and provides functions such as authentication, mobility management,charging and so on. Regarding terminology, terminal devices may also bereferred to as mobile stations, user equipment (UE), user terminal,terminal, mobile radio, mobile terminal, mobile device, or simplydevice, and so forth. Base stations may also be referred to transceiverstations, nodeBs, e-nodeBs, eNBs and so forth.

FIG. 1A shows a schematic representation of an example of a userequipment 104. The user equipment 104 comprises a transceiver unit 104Afor transmission and reception of wireless signals and a processor unit104B configured to control the user equipment. The processor unit 104Bmay comprise various sub-units for providing functionality in accordancewith embodiments of the present disclosure as explained further herein.These sub-units may be implemented as discrete hardware elements or asappropriately configured functions of the processor unit. Thus theprocessor unit 104B may comprise a processor unit which is suitablyconfigured/programmed to provide the desired functionality describedherein using conventional programming/configuration techniques forequipment in wireless telecommunications systems. The transceiver unit104A and the processor unit 104B are schematically shown on FIG. 1A asseparate elements for ease of representation. However, it will beappreciated that the functionality of these units can be provided invarious different ways, for example using a single suitably programmedgeneral purpose computer, or suitably configured application-specificintegrated circuit(s)/circuitry. It will be appreciated that the userequipment will in general comprise various other elements associatedwith its operating functionality, for example a power source, userinterface, and so forth, but these are not shown in FIG. 1A in theinterests of simplicity.

FIG. 1B shows a schematic representation of an example of a base station101. In a network such as that in FIG. 1, each base station 101 may befunctionally identical but each serves one or more differentgeographical area (cells 103). In some examples, base stations may beconfigured for operation in different related, or interworking,architectures, in an arrangement known as dual connectivity. In general,though, each base station 101 comprises a transceiver unit 101A fortransmission and reception of communications between the base stationand any user equipment 104 in its cell, and the core network 102. A basestation 101 further comprises a processor unit 101B configured tocontrol the base station 101 to operate in accordance with embodimentsof the present disclosure as described herein. The processor unit 101Bmay again comprise various sub-units for providing functionality inaccordance with embodiments of the present disclosure as explainedherein. Theses sub-units may be implemented as discrete hardwareelements or as appropriately configured functions of the processor unit.Thus, the processor unit 101B may comprise a processor unit which issuitably configured/programmed to provide the desired functionalitydescribed herein using conventional programming/configuration techniquesfor equipment in wireless telecommunications systems. The transceiverunit 101A and processor unit 101B are schematically shown in FIG. 1B asseparate elements for ease of representation. However, it will beappreciated that the functionality of these units can be provided invarious different ways, for example using a single suitably programmedgeneral purpose computer, or suitably configured application-specificintegrated circuits(s)/circuitry. It will appreciated that the basestation 101 will in general comprise various other elements, for examplea power supply, associated with its operating functionality.

In particular, the processor units of user equipment and base stationsinclude resources for handling radio bearers. The resources may includea protocol stack comprising layers including a PDCP (packet dataconvergence protocol), a RLC (radio link control) and a MAC (mediumaccess control), where the layers may be dedicated to particular typesof radio bearer, or may be shared. Under particular events in thenetwork operation, one or more parts of the resources may need to bereset or re-established for continued operation, which herein isreferred to generally as reconfiguration, or alternatively asalteration, indicating some change in in the resources, includingresetting, re-establishment, clearing, removing from use and other likeprocedures that alter the way in which the resources are able to handleone or more radio bearer types. The procedures for resetting andre-establishing are well-understood, and specified in the 3GPPstandards. For example, the MAC reset procedure is specified in section5.9 of 3GPP specification TS 36.321, the RLC re-establishment procedureis specified in section 5.4 of 3GPP specification TS 36.322, and thePDCP re-establishment is specified in section 5.2 of 3GPP specificationTS 36.323. On a high level, a layer is reset during reset orre-establishment, but different terminology is used in the differentspecifications for the various protocol layers.

As is well understood, in wireless telecommunications networks such asan LTE type network, there are different Radio Resource Control (RRC)modes for terminal devices, including governing the connection statebetween the terminal device and a base station. These include an idlemode and a connected mode. Generally speaking, in RRC connected mode aterminal device is connected to a base station in the sense of beingable to receive user plane data from the base station, whereas in RRCidle mode the terminal device is unconnected to a base station in thesense of not being able to receive user plane data from the basestation. However, in idle mode the terminal device may still receivesome communications from base stations, for example, referencesignalling for cell reselection purposes and other broadcast signalling.

While the FIG. 1 example network shows all base stations (eNBs) as beingthe same, and each supporting one cell, in some networks and systemsother arrangements may be used. For example, in Release 12 of the 3GPPstandard governing the LTE architectures, the concept of dualconnectivity (DC) was introduced. In dual connectivity, base stationsare specified as being either a master base station or a secondary basestation, and user equipment can connect with both.

FIG. 2 shows a schematic representation of the control planearchitecture specified for dual connectivity. A master base station 105(designated MeNB) and a secondary base station 106 (designated SeNB)communicate via a control plane using X2-C layer protocol. However,unlike the description above in which any base station is involved inhandling RRC communications, in dual connectivity only the MeNB 105 isdesignated for RRC handling Consequently, the RRC entity resides in theMeNB 105, and communication with the core network in the form of amobility management entity 107 (MME) via an S1-MME protocol layerterminates in the MeNB 105.

Also, it is possible for a base station, being a master or a secondaryeNB, to support more than one cell. FIG. 3 shows a schematicrepresentation of part of a network having a MeNB 105 supporting threecells 105A, 105B and 105C, and a SeNB 106 supporting three cells 106A,106B and 106C. A user equipment UE 104 has access to cells from botheNBs, indicated as the group 108. Within the group 108, one cell can bea primary cell, from the MeNB cells. Within the group 108 relating tothe UE 104, the MeNB cells 105A and 105B are designated as a master cellgroup MCG, and the SeNB cells 106A and 106B are designated as asecondary cell group SCG. The UE 104 has access to the cells of MCG andthe two cells of the SCG, indicated by the overlapping cell areas inFIG. 3.

A purpose of the dual connectivity arrangement is to enable sharing andcombining of resources belonging to different base stations. Thissharing is expressed in the concept of split bearers.

FIG. 4 show a schematic representation of an example user plane protocolstack for a dual connectivity arrangement. Typically, an incomingmessage arrives via a bearer and is handled by the various protocollayers defined within the LTE architecture. Once master and secondaryeNBs are defined and grouped in dual connectivity, one can furtherdesignate a bearer intended for the MeNB 105 as a master cell groupbearer, MCG bearer 109, and a bearer intended for the SeNB 106 as asecondary cell group bearer, SCG bearer 110. A bearer arrives via the S1protocol layer, is handled by the eNB's resources in turn by a packetdata convergence protocol (PDCP), then a radio link control (RLC)protocol, and then the medium access control (MAC) layer. As shown inFIG. 4, each eNB 105, 106 has these resource layers to handle receivedbearers.

In addition to the MCG bearer and the SCG bearer, dual connectivitydefines a third, split bearer, for the purpose of sharing resources inthe MeNB and the SeNB on the network side of the telecommunicationssystem. A split bearer 111 is delivered to a PDCP in the MeNB 105, andthe MeNB 105, at the PDCP, then controls a split or division of thesplit bearer's data between the MeNB 105 and the SeNB 106. Data for theMeNB 105 is passed to the MeNB's RLC and then its MAC, and data for theSeNB 106 is passed from the MeNB 105, using the X2 protocol layer, to anRLC in the SeNB and then to the MAC of the SeNB.

In order to be able to handle a message carried by a split bearer onceit is passed on from the two eNBs, a UE is provided with two MACentities, a master cell group MAC (MCG MAC) and a secondary cell groupMAC (SCG MAC), plus corresponding RLC and PDCP. These are included inthe resources of the UE for split bearer handling.

As mentioned above, only the MeNB has a RRC entity, so signalling radiobearers for RRC are transported over the MCG only, i.e. by MCG bearer.The SCG is not involved in the transporting of RRC messages. For UEsconfigured for dual connectivity and split bearer transport, usertraffic from the core network can be received at the MeNB as a splitbearer, and then divided between the MeNB and the SeNB for handling andpassing to the UE. Any traffic on a SCG bearer is received from the corenetwork at the SeNB and transported using resources of the SeNB to theUE.

In the context of LTE, further details regarding dual connectivity canbe found in the 36.300 specification at sections 6.5 and 7.6, and alsoin 3GPP TR 36.842.

As can be seen from FIG. 4, a bearer arrives at the PDCP protocol layer.The PDCP is involved in security of the data traffic, includingciphering using a key. Each PDCP in each network entity (eNBs and UEs,for example) will use its own key; these are regularly updated. The MeNBmay use a key designated as KeNB, while the SeNB may use a keydesignated as SKeNB. Other parameters are utilised by the PDCP togetherwith the key to effect security; these include a numerical counter togenerate successive numbers in a sequence of count values. Hence thereis a set of parameters, used in a security algorithm to perform theciphering. Each set of parameters, one for each successive number fromthe count value, is used only once for ciphering, to maintain security.The count value has a maximum number that can be generated, so for agiven key, once this number is reached, there are no new parameter setsavailable for ciphering. Re-use of parameters is undesirable, so it ispreferred to acquire a new key for the PDCP and start the count valuesequence again at its beginning (at zero, for example), to work throughall successive values in the count value sequence with the new key. Theexpiration of the numbers available from the counter can be referred toas “rollover”, and hereinafter the disclosure may mention “PDCProllover”, “PDCP counter rollover”, “PDCP count rollover or “countrollover”. The process following rollover, including acquisition of anew key, has a high processing overhead associated with it, and requiresa resetting of the MAC layer for handling of ciphering with the new key.

An example of a possible network configuration for futuretelecommunications is an arrangement comprising an LTE architectureproviding wide (macro) coverage in conjunction with a so-called newradio (NR), referring to current and future telecommunications methodsallowing increased data throughput, such as 4th and 5th generations (4Gand 5G) and further. The type of radio access technology (RAT) used inthe LTE network and the new radio network may be different, but an LTEnetwork and a NR network could interwork, where a benefit of havingconnectivity to both LTE and NR is reduced signalling towards the corenetwork from mobility towards the core network being anchored at the LTEmacro entity, combined with higher throughput made possible be utilisingresources in both LTE and NR. A UE will be configured to operate underboth RATs. In this context, dual connectivity is relevant, such thatMeNBs may be designated from LTE and SeNBs from NR, or vice versa.

Split bearers are therefore also relevant, and a new split bearerconfiguration is considered, namely a secondary cell group split bearer,or SCG split bearer.

FIG. 5 shows a schematic representation of an example user planeprotocol stack utilising a SCG split bearer. As in FIG. 4, a master node105 (in this example in the LTE side) and a secondary node 106 eachreceive their designated bearers, MCG bearer 109 and SCG bearer 110respectively, and these are handled by a PCDP, a RLC and a MAC layer, asbefore. No conventional split bearer is included, however; instead thereis a SCG split bearer 112 which is delivered to the SeNB 106 (labelledSecondary gNB in FIG. 5 to indicate a difference from the eNB of FIG. 4owing to the addition of the NR network). A PDCP in the SeNB 106receives the SCG split bearer 112 and divides the data. Some is retainedin the SeNB, being passed to the RLC and MAC layers. Other data ispassed from the SeNB 106 to the MeNB 105 via an X protocol layer(labelled Xnew to indicate possible change from the X layers within LTE,such as the X1 layer in FIG. 4), and the MeNB 105 handles it with itsown RLC and MAC resources.

The SCG split bearer is proposed in the context of the higher data ratesthat can be handled in an NR architecture. Note this is merely anexample, however, and secondary cell group split bearers are relevant inother contexts also.

FIG. 5 shows SCG split and SCG bearers together, and they may besimultaneously used or supported. SCG bearer can be considered as aspecial case of SCG split bearer, in which 100% of the data traffic isover the SCG and 0% over the MCG. Either or both of the SCG bearer andthe SCG split bearer may coexist alongside the MCG bearer. Coexistenceof the MCG split bearer (as in the FIG. 4 example) and the SCG splitbearer is possible despite different transport requirements duringRel-12 DC and hence a need for a high bandwidth in the user planeanchor. However, any coexistence of bearer types is not relevant to thepresent disclosure, and embodiments and examples addressing the SCGsplit bearer can be implemented regardless of other secondary nodebearers.

However, the coexistence of the MCG bearer and the SCG split bearerimplies that there will be at least one PDCP entity in the MCG, tohandle the MCG bearer, and at least one PDCP entity in the SCG, tohandle the SCG split bearer. Consequently, ciphering will be carried outusing two keys, the KeNB in the MCG PDCP and the SKeNB in the SCG PDCP.The MeNB MAC receives data ciphered with both keys.

Recall the above discussion that mentioned PDCP count rollover. Under3GPP Release 12 for dual connectivity, a “SCG change” procedure isdefined for situations including a rollover of the SeNB PDCP receivingthe SCG bearer. This is defined in section 10.1.2.8.6 of the 36.300standard, and includes the requirement that “During SCG change, MACconfigured for SCG is reset and RLC configured for SCG is re-establishedregardless of the bearer type(s) established on SCG. For SCG bearer,PDCP configured for SCG is re-established. In case of reconfigurationfrom split to MCG bearer, RLC configured for SCG is released. During SCGchange, S-KeNB key is refreshed.”

The SCG change procedure is applicable in a range of scenarios. FIG. 6shows a depiction of a SeNB modification procedure which uses the SCGchange procedure, from standard 36.300 section 10.1.2.8.2.

This scope of SCG change procedure is restricted to cells under controlof the SeNB, and therefore in the SCG. However, a SCG split bearer willuse a RLC instance in the MCG (see FIG. 5), and share the MCG MAC withother MCG bearers including SRBs (signalling radio bearers, for RRCsignalling). An SCG SRB may be configured in addition using SCG MAC soboth MAC entities are involved in handling of signalling radio bearersin case of LTE-NR dual connectivity. Also, note that in any changebetween MCG bearer and (conventional) split bearer there will be no needto reset any of the MCG resources because ciphering for both bearers isdone in MCG PDCP (see FIG. 4), and MCG RLC and MCG MAC can continuewithout any reset. This is not possible for the SCG split bearer,however, because the SCG PDCP in the SeNB will cipher the SCG splitbearer, before passing it to resources in the MCG (RLC and MAC in theMeNB).

Hence, a difficulty can arise for SCG split bearers when a PDCP countrollover occurs in the SeNB. Recall from above that a count rolloverinitiates the SCG change procedure, which includes refreshing of theSKeNB key. Resources in the MeNB may then be unable to handle theirallocated part of the SCG split bearer.

Standard 36.300, section 14.1 specifies PDCP count in dual connectivityas: SCG bearers in DC share a common pool of radio bearer identities(DRB IDs) together with the MCG bearers and when no new DRB ID can beallocated for an SCG bearer without guaranteeing COUNT reuse avoidance,the MeNB shall derive a new S-K_(eNB). SeNB indicates to MeNB whenuplink or downlink PDCP COUNTs are about to wrap around and MeNB shallupdate the S-K_(eNB). To update the S-K_(eNB), the MeNB increases theSCG Counter and uses it to derive a new S-K_(eNB) from the currentlyactive KeNB in the MeNB. The MeNB sends the newly derived S-K_(eNB) tothe SeNB. The newly derived S-K_(eNB) is then used by the SeNB incomputing a new encryption key K_(UPenc) which is used with all DRBs inthe SeNB for this UE. Furthermore, when the SCG Counter approaches itsmaximum value, the MeNB refreshes the currently active KeNB, before anyfurther S-K_(eNB) is derived.

From this we can appreciate that in the event of PDCP rollover for a SCGsplit bearer, it is required that the SCG change procedure should beinitiated for the resources under the SeNB, i.e. SCG RLC and PDCP shouldbe re-established and the SCG MAC is reset. In the scenario of LTR-NRinterworking described above, it is likely that PDCP count rollover willhappen in the NR PDCP (in other words, the SeNB, as in FIG. 5), becausethe majority of the data traffic will be pushed using NR (rather thanLTE) to take advantage of the higher throughput. Accordingly, followinga similar logic, and because SCG split bearer data packets will beciphered by the SCG PDCP, rollover of the SCG PDCP suggest a requirementfor a change procedure in which the MCG RLC should be re-established,and the MCG MAC should also be reset.

Consequently, a proposal to address the issue of PDCP rollover in theSeNB when SCG split bearers are used, as disclosed in co-pendingEuropean patent application no. EP16191055, is to ensure thatappropriate handling of the MCG resources is undertaken, which in someexamples includes resetting/re-establishing of the MCG RLC and the MCGMAC. Some of these proposals include proposals which seek to avoid anMCG MAC reset.

FIG. 7 shows a ladder diagram indicating steps in a first proposal of amethod to achieve this. A network and its entities are configured forSCG split bearer use. For example, the entities comprise a UE 104, aMeNB 105 in a LTE architecture and a SeNB 106 in a NR architecture. In afirst step S1, PDCP count rollover is recognised in the SeNB 106. Instep S2, the SeNB 106 indicates to the MeNB 105 that PDCP rollover hasoccurred so that SeNB resource modification (reconfiguration) isrequired. In response, the MeNB 105 creates a new security key for theSeNB 106, and sends it to the SeNB 106 in step S3. Note that steps S1,S2 and S3 are the same as in the known SCG change procedure. Under theproposal, however, a next step S4 requires the SeNB 106 to additionallyindicate to the MeNB 105 that handling (modification, reconfiguration)of the MCG resources relevant to the SCG split bearer is required, sothat the MCG RLC and the MCG MAC are to be reset; the MeNB 105 performsthis. Finally, in Step S5, the MeNB 105 carries out RRC reconfigurationof the UE 104. This also occurs in the SCG change procedure, in that theUE's SCG MAC is reset and its SCG RLC is re-established, butadditionally here the UE's MCG MAC is reset and its MCG RLC isre-established (recall that the UE is provided with resources for boththe MCG and the SCG for operation under dual connectivity, so it has twoMAC entities, for example). The UE's SCG PDCP for the split SCG beareris also re-established.

However, this solution presents issues in that resetting the MCG MACwill impact the SRBs and DRBs (signalling and data radio bearers)arriving at the MCG. The RLC in the MeNB should not be affected becausethere is a single instance of RLC per RB. However the MAC layer isconfigured for a whole cell group (MCG or SCG). Consequently, it wouldbe preferable to avoid resetting the MAC. It is equivalent to moving theUE to RRC idle state, which is clearly problematic.

On the other hand, if the MCG MAC is not reset, one consequence is thatthere may be data packets (herein also “packets”) in the MCG MAC HARQbuffer for the SCG split bearer which will halt a HARQ process or makeit unusable. HARQ, or hybrid automatic repeat request, combineshigh-rate forward error correcting coding and ARQ error control, and isa process undertaken in the MAC, taking packets stored in the HARQbuffer. Such a scenario is shown in FIG. 8, where it can be seen that,due to not having been received successfully before re-establishment, apacket with a sequence number (SN) of 2 is retransmitted successfullyafter re-establishment, along with a second packet with an SN of 2.Resetting the MAC clears the buffer, and hence addresses any halt orunusability of a HARQ process. As a consequence, it is important toconsider carefully the prospect of resetting or not resetting the MCGMAC to address an SCG PDCP count rollover.

A second proposal as disclosed in co-pending European patent applicationno. EP16191055, the contents of which are incorporated herein byreference. The arrangement disclosed in EP16191055 provides analternative to that in FIG. 7, is to not reset the MCG MAC, and limitthe handling of the MCG resources to a re-establishment of the MCG's RLCfor SCG split bearer only. DRB release for conventional bearers does notinvolve a MAC reset, so omitting this procedure is feasible. Notehowever that it is assumed that there will be no packets queued in theHARQ for a bearer about to be released so that all processes continue asusual for the remaining DRBs.

A benefit of not resetting the MCG MAC for a SCG split bearer is thatthere will be no interruption of traffic on the MCG side of the link.However, there may be packets in the MCG MAC related to the SCG splitbearer. An option to manage these is to continue with thetransmission/reception until the HARQ processes have cleared, forexample by setting a timer for the HARQ operation so that it is assumedto have cleared when the timer expires. Then, the MCG MAC discards anyremaining packets related to the SCG split bearer after the MCG RLC hasbeen re-established and the timer has expired (or the HARQ queue isotherwise empty or deemed empty).

A MAC reset is not limited only to PDCP Count rollover. It may alsoinclude bearer type switching, which involves handling of L2 protocolsincluding MCG and SCG-MAC. A proposal relating to allowed bearer typechange options in RAN2 #97bis is summarised as follows:

-   -   LTE-NR DC should support at least the following bearer type        change options        -   MCG bearer to/from MCG split bearer,        -   MCG bearer to/from SCG bearer,        -   MCG bearer to MCG bearer,        -   SCG bearer to SCG bearer,        -   MCG split bearer to MCG split bearer    -   LTE-NR DC should not support the direct bearer type change        between MCG split bearer and SCG bearer.    -   LTE-NR DC should support the one step bearer type change between        MCG bearer to/from SCG split bearer.    -   LTE-NR DC shall support the bearer type change between SCG        bearer and SCG split bearer.    -   LTE-NR DC should support the bearer type change between SCG        split bearer and SCG split bearer.    -   LTE-NR DC may also support the direct type change between MCG        split bearer to/from SCG split bearer.

In the following scenarios, where traditionally in Rd-12, DC MAC wasreset, it can be envisaged that a MAC reset should not be required:

-   -   MCG to MCG change due to security when KeNB refresh is needed.        This procedure relied on intra cell handover and all protocol        entities were reset. In embodiments of the present technique,        MCG-PDCP and MCG-RLC will still be re-established but MAC entity        survives reset.    -   A similar situation as above occurs for SCG to SCG change due to        security. This case is similar to EP16191055, but EP16191055        focused only on SCG split bearer.    -   The main focus of EP16191055 was the question of whether the L2        handling in Table I (taken from the discussion related to the        RAN2 #97bis meeting) below can be used for LTE NR DC for SCG        bearer to/from SCG split bearer and changed due to security.    -   Scenario of whether the L2 handling in Table II (taken from the        discussion related to the RAN2 #97bis meeting) below can be used        for LTE NR DC for SCG split bearer to/from SCG split bearer was        not considered in EP16191055.    -   All other scenarios where SCG MAC is reset based on SCG Change        procedure.

TABLE I SCG bearer to/from SCG split Bearer Bear type change MCG/SCGPDCP RLC/DTCH MAC SCG to MCG part N/A establish No impact SCG split SCGpart Reestablished Reestablished reset (SCG (SCG change) (SCG change)change) SCG split MCG part N/A Release No impact to SCG SCG partRelease? Reestablished reset (SCG (SCG change) change)

TABLE II SCG split bearer to/from SCG split bearer Bear type changeMCG/SCG PDCP RLC/DTCH MAC SCG split MCG part N/A reestablish No impactto SCG SCG part Reestablished Reestablished reset (SCG split (SCGchange) (SCG change) change)

Embodiments of the present technique address how to avoid the reset ofthe MAC entity when the upper L2 sublayers (i.e. RLC and PDCP entities)are re-established. As previously described in EP16191055, the resettingof MCG MAC disrupts SRBs and so should be avoided. However,re-establishing RLC without a MAC reset will mean that there may beresidual data leftover in the MAC layer. For example RLC PDUs which havebeen transmitted (by RLC) are sitting in the HARQ transmission buffer inMAC because for example HARQ ACK has not yet been received. These PDUsneed to be retransmitted by the MAC layer. The problem with this is thatit becomes ambiguous to the RLC layer whether the PDU SN corresponds tothe SN after resetting to 0, or if it belongs the SN of PDUs that weretransmitted before RLC re-establishment. This is a particular problem ifthe SN before RLC re-establishment is a low value. When the SN is resetto 0, it is not clear whether the SN related to before or after reset.The receiving RLC entity needs to know, so that SDUs can be reassembledand passed to PDCP layer.

EP16191055 covered RRC/MAC/PHY signaling and RLC status report basedsolutions. These solutions may require extra signaling and does notexplicitly cover a new field in RLC header.

Embodiments of the present technique serve to introduce a new bit in anRLC packet header. The bit is toggled in the transmitter RLC entityafter RLC sublayer is re-established and included in the header field ofall RLC PDUs generated after reestablishment. This bit will ensure thata MAC entity continues the operation and transmit/retransmit HARQsegments as normal. The receiving HARQ entities will receive HARQsegments and prepare RLC PDUs as normal. RLC PDUs which have beenprepared before RLC entity reestablishment will either have no new bitor e.g. include a bit set to “0”. RLC PDUs sent by the RLC transmitentity after reestablishment will either include a new bit or toggle thebit to “1”. FIG. 9 demonstrates a process according to embodiments ofthe present technique. Unlike in FIG. 8, where followingre-establishment, two identical packets or PDUs with an SN of 2 arereceived, it is clear from a difference in the toggled bit which of thePDUs with SN=2 should have been received before the re-establishment andwhich of the PDUs with SN=2 was transmitted before the re-establishment.

In other words, such embodiments of the present technique disclose amethod for use in a mobile communications network, the mobilecommunications network comprising a plurality of infrastructureequipment each providing wireless connectivity within at least one cell,and a communications device configured to communicate wirelessly with atleast a first of the infrastructure equipment including by the use of aradio bearer, the method comprising the first infrastructure equipmentdetermining that there is a requirement to alter data handling resourcesallocated for handling the radio bearer in one or both of the firstinfrastructure equipment and the communications device, re-establishing,in response to the determination, its radio link control protocol layer(and/or PDCP layer), transmitting a reconfiguration message to thecommunications device to effect re-establishment of its radio linkcontrol protocol layer (and/or PDCP layer), and subsequently effecting achange in the header of (RLC) data packets transmitted to thecommunications device.

In some embodiments of the present technique, the cells are arrangedinto a master cell group under control of the first infrastructureequipment, the first infrastructure equipment being a masterinfrastructure equipment, and a secondary cell group under control of asecondary infrastructure equipment, and the communications device isconfigured to communicate wirelessly with the master infrastructureequipment and the secondary infrastructure equipment, and the radiobearer is configured in dual connectivity and receivable at thesecondary infrastructure equipment for splitting between the secondaryinfrastructure equipment and the master infrastructure equipment beforedelivery to the communications device. The determining that there is arequirement to the alter data handling resources may comprise receivingat the master infrastructure equipment a notification transmitted by thesecondary infrastructure equipment when the secondary infrastructureequipment exhausts a supply of unique parameter sets used in securityciphering of received radio bearers configured in dual connectivity.

In some embodiments of the present technique, the cells are arrangedinto a master cell group under control of a master infrastructureequipment and a secondary cell group under control of the firstinfrastructure equipment, the first infrastructure equipment being asecondary infrastructure equipment, and the communications device isconfigured to communicate wirelessly with the master infrastructureequipment and the secondary infrastructure equipment, and the radiobearer is configured in dual connectivity and receivable at thesecondary infrastructure equipment for splitting between the secondaryinfrastructure equipment and the master infrastructure equipment beforedelivery to the communications device. The determining that there is arequirement to the alter data handling resources may comprise exhaustingat the secondary infrastructure equipment a supply of unique parametersets used in security ciphering of received radio bearers configured indual connectivity.

In some embodiments of the present technique, there is also defined amethod for use in a mobile communications network, the mobilecommunications network comprising a plurality of infrastructureequipment each providing wireless connectivity within at least one cell,wherein the cells are arranged into a master cell group under control ofa master infrastructure equipment and a secondary cell group undercontrol of a secondary infrastructure equipment, and a communicationsdevice is configured to communicate wirelessly with the infrastructureequipment including by the use of a split radio bearer receivable at thesecondary infrastructure equipment for splitting between the secondaryinfrastructure equipment and the master infrastructure equipment beforedelivery to the communications device. The method comprises, when thesecondary infrastructure equipment exhausts a supply of unique parametersets used in security ciphering of received split radio bearers, thesecondary infrastructure equipment sending a notification to the masterinfrastructure equipment of a requirement to alter data handlingresources allocated for handling split radio bearers received from thesecondary infrastructure equipment in one or both of the masterinfrastructure equipment and the communications device, and the masterinfrastructure equipment, in response to the notification,re-establishing its radio link control protocol layer and transmitting areconfiguration message to the communications device to effectre-establishment of its radio link control protocol layer, andsubsequently effecting a change in the header of data packetstransmitted to the communications device. The change in the header ofthe data packets comprises the addition of a new bit, or comprisestoggling the value of a bit.

RLC receive entity may receive RLC PDU with same RLC SN before or afterthe reestablishment and the new bit will help receiver to discard theright packet i.e. the one with no toggle bit and keep the packet withtoggled bit. This is visually demonstrated in FIG. 10. In other words,the communications device re-establishes its radio link control protocollayer in response to the reconfiguration message, and subsequentlydiscards from a buffer of the communications device one or more datapackets with headers that have not been changed by the masterinfrastructure equipment in response to the notification.

As an alternative to discarding the PDUs which correspond totransmissions before the RLC re-establishment, the UE may continue toattempt to reassemble those PDUs to form SDUs that can be passed to PDCPeither by maintaining a separate buffer within the same RLC entity, orcreating a duplicate RLC entity to handle PDUs from before and afterre-establishment (which can avoid retransmissions from the upperlayers—particularly a problem due to TCP slow start mechanisms. TCPinterprets retransmissions as having been caused by network congestion,since it was initially designed for fixed line communication systems,and therefore the data rate slows upon any retransmissions, affectingthe throughput temporarily). In other words, the communications devicere-establishes its radio link control protocol layer in response to thereconfiguration message, and subsequently, controls the storage ofreceived data packets with headers that have or have not been changed bythe master infrastructure equipment in response to the notification inseparate buffers of the communications device. Alternatively, thecommunications device duplicates a radio link control entity of thecommunications device, the radio link control entity and the duplicateradio link control entity being used to separately handle received datapackets with headers that have or have not been changed by the masterinfrastructure equipment in response to the determination.Alternatively, or additionally, the communications device duplicates apacket data convergence protocol entity of the communications device,the packet data convergence protocol entity and the duplicate packetdata convergence protocol being used to separately handle received datapackets with headers that have or have not been changed by the firstinfrastructure equipment in response to the determination.

In embodiments of the present technique, the infrastructure equipmentand communications device may each comprise transmitter circuitryconfigured to transmit signals, receiver circuitry configured to receivesignals, and controller circuitry configured to control the transmittercircuitry and the receiver circuitry. The controller circuitry may be,for example, a microprocessor, a CPU, or a dedicated chipset, etc. Itwill be appreciated by those skilled in the art that, in arrangements ofthe present technique, the communications device/UE may not alwaysinclude a transmitter, for example in scenarios where the UE is alow-power wearable device.

Embodiments of the present technique apply to LTE RLC for example toapplications such as new radio to improve LTE-NR interworking where LTEis master node and MCG-MAC is not reset due to MCG-RLC reestablishment.In other words, the master infrastructure equipment and the secondaryinfrastructure equipment operate in accordance with the same radioaccess technology. Embodiments of the present technique also apply to NRRLC in case of NR-NR multi connectivity and LTE-NR improved interworkingwhen SCG-MAC is not reset due to SCG-RLC reestablishment. In otherwords, the master infrastructure equipment and the secondaryinfrastructure equipment operate in accordance with different radioaccess technologies.

Advantages of the present technique include that the MAC entity cancontinue the operation when upper layers have been re-established,avoiding the disruption of SRBs or SCG bearers, and avoiding anyambiguity at the RLC layer after re-establishment due to residual PDUsleft over in MAC.

These examples may also be applied for mobility within a NR MCG as well.It has been assumed in these examples that LTE is the master and NR isthe secondary, operating in accordance with LTE-NR improvedinterworking. For a deployment where NR is master and LTE is secondary,it is assumed that NR CU-DU split may happen and LTE may or may notsupport C-RAN architecture. No difference is foreseen between the twocases. In further arrangements of the present technique, NR may be boththe master and the secondary, operating in accordance with NR-NRmulti-connectivity.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, define, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

The following numbered paragraphs provide further example aspects andfeatures of the present technique:

Paragraph 1. A method for use in a mobile communications network, themobile communications network comprising

-   -   a plurality of infrastructure equipment each providing wireless        connectivity within at least one cell, and    -   a communications device configured to communicate wirelessly        with at least a first of the infrastructure equipment including        by the use of a radio bearer, the method comprising the first        infrastructure equipment    -   determining that there is a requirement to alter data handling        resources allocated for handling the radio bearer in one or both        of the first infrastructure equipment and the communications        device,    -   re-establishing, in response to the determination, its radio        link control protocol layer,    -   transmitting a reconfiguration message to the communications        device to effect re-establishment of its radio link control        protocol layer, and subsequently    -   effecting a change in the header of data packets transmitted to        the communications device.

Paragraph 2. A method according to Paragraph 1, wherein the cells arearranged into a master cell group under control of the firstinfrastructure equipment, the first infrastructure equipment being amaster infrastructure equipment, and a secondary cell group undercontrol of a secondary infrastructure equipment, and the communicationsdevice is configured to communicate wirelessly with the masterinfrastructure equipment and the secondary infrastructure equipment, and

-   -   wherein the radio bearer is configured in dual connectivity and        receivable at the secondary infrastructure equipment for        splitting between the secondary infrastructure equipment and the        master infrastructure equipment before delivery to the        communications device.

Paragraph 3. A method according to Paragraph 2, wherein the determiningthat there is a requirement to the alter data handling resourcescomprises receiving at the master infrastructure equipment anotification transmitted by the secondary infrastructure equipment whenthe secondary infrastructure equipment exhausts a supply of uniqueparameter sets used in security ciphering of received radio bearersconfigured in dual connectivity.

Paragraph 4. A method according to Paragraph 1, wherein the cells arearranged into a master cell group under control of a masterinfrastructure equipment and a secondary cell group under control of thefirst infrastructure equipment, the first infrastructure equipment beinga secondary infrastructure equipment, and the communications device isconfigured to communicate wirelessly with the master infrastructureequipment and the secondary infrastructure equipment, and

-   -   wherein the radio bearer is configured in dual connectivity and        receivable at the secondary infrastructure equipment for        splitting between the secondary infrastructure equipment and the        master infrastructure equipment before delivery to the        communications device.

Paragraph 5. A method according to Paragraph 4, wherein the determiningthat there is a requirement to the alter data handling resourcescomprises exhausting at the secondary infrastructure equipment a supplyof unique parameter sets used in security ciphering of received radiobearers configured in dual connectivity.

Paragraph 6. A method according to any of Paragraphs 1 to 6, wherein thechange in the header of the data packets comprises the addition of a newbit.

Paragraph 7. A method according to Paragraph 6, wherein the new bit isadded to the header of the data packets for a predetermined time afterthe re-establishment of the radio link control protocol layer of thefirst infrastructure equipment.

Paragraph 8. A method according to any of Paragraphs 1 to 7, wherein thechange in the header of the data packets comprises toggling the value ofa bit.

Paragraph 9. A method according to Paragraph 8, wherein the value of thebit is toggled for a predetermined time after the re-establishment ofthe radio link control protocol layer of the first infrastructureequipment.

Paragraph 10. A method according to any of Paragraphs 1 to 9, whereinthe communications device re-establishes its radio link control protocollayer in response to the reconfiguration message, and subsequentlydiscards from a buffer of the communications device one or more datapackets with headers that have not been changed by the firstinfrastructure equipment in response to the determination.

Paragraph 11. A method according to any of Paragraphs 1 to 10, whereinthe communications device re-establishes its radio link control protocollayer in response to the reconfiguration message, and subsequently,controls the storage of received data packets with headers that have orhave not been changed by the first infrastructure equipment in responseto the determination in separate buffers of the communications device.

Paragraph 12. A method according to any of Paragraphs 1 to 11, whereinthe communications device duplicates a radio link control entity of thecommunications device, the radio link control entity and the duplicateradio link control entity being used to separately handle received datapackets with headers that have or have not been changed by the firstinfrastructure equipment in response to the determination.

Paragraph 13. A method according to any of Paragraphs 1 to 12, whereinthe communications device duplicates a packet data convergence protocolentity of the communications device, the packet data convergenceprotocol entity and the duplicate packet data convergence protocol beingused to separately handle received data packets with headers that haveor have not been changed by the first infrastructure equipment inresponse to the determination.

Paragraph 14. A method according to any of Paragraphs 2 to 13, whereinthe master infrastructure equipment and the secondary infrastructureequipment operate in accordance with the same radio access technology.

Paragraph 15. A method according to any of Paragraphs 2 to 13, whereinthe master infrastructure equipment and the secondary infrastructureequipment operate in accordance with different radio accesstechnologies.

Paragraph 16. A mobile communications network comprising

-   -   a plurality of infrastructure equipment each providing wireless        connectivity within at least one cell, and    -   a communications device configured to communicate wirelessly        with at least a first of the infrastructure equipment including        by the use of a radio bearer, wherein the first infrastructure        equipment is configured    -   to determine that there is a requirement to alter data handling        resources allocated for handling the radio bearer in one or both        of the first infrastructure equipment and the communications        device,    -   to re-establish, in response to the determination, its radio        link control protocol layer,    -   to transmit a reconfiguration message to the communications        device to effect re-establishment of its radio link control        protocol layer, and subsequently    -   to effect a change in the header of data packets transmitted to        the communications device.

Paragraph 17. Circuitry for a mobile communications network comprising

-   -   a plurality of infrastructure equipment each providing wireless        connectivity within at least one cell, and    -   a communications device configured to communicate wirelessly        with at least a first of the infrastructure equipment including        by the use of a radio bearer, wherein the first infrastructure        equipment is configured    -   to determine that there is a requirement to alter data handling        resources allocated for handling the radio bearer in one or both        of the first infrastructure equipment and the communications        device,    -   to re-establish, in response to the determination, its radio        link control protocol layer,    -   to transmit a reconfiguration message to the communications        device to effect re-establishment of its radio link control        protocol layer, and subsequently    -   to effect a change in the header of data packets transmitted to        the communications device.

Paragraph 18. An infrastructure equipment for use in a mobilecommunications network, the mobile communications network comprising oneor more other infrastructure equipment, the infrastructure equipment andother infrastructure equipment each providing wireless connectivitywithin at least one cell, and a communications device configured tocommunicate wirelessly with the infrastructure equipment including bythe use of a radio bearer, wherein the infrastructure equipmentcomprises

-   -   transmitter circuitry configured to transmit signals to the        communications device and to the other infrastructure equipment,    -   receiver circuitry configured to receive signals from the        communications device and from the other infrastructure        equipment, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry    -   to determine that there is a requirement to alter data handling        resources allocated for handling the radio bearer in one or both        of the infrastructure equipment and the communications device,    -   to re-establish, in response to the determination, its radio        link control protocol layer,    -   to transmit a reconfiguration message to the communications        device to effect re-establishment of its radio link control        protocol layer, and subsequently    -   to effect a change in the header of data packets transmitted to        the communications device.

Paragraph 19. A method of operating an infrastructure equipment for usein a mobile communications network, the mobile communications networkcomprising one or more other infrastructure equipment, theinfrastructure equipment and other infrastructure equipment eachproviding wireless connectivity within at least one cell, and acommunications device configured to communicate wirelessly with theinfrastructure equipment including by the use of a radio bearer, whereinthe method comprises

-   -   determining that there is a requirement to alter data handling        resources allocated for handling the radio bearer in one or both        of the infrastructure equipment and the communications device,    -   re-establishing, in response to the determination, its radio        link control protocol layer,    -   transmitting a reconfiguration message to the communications        device to effect re-establishment of its radio link control        protocol layer, and subsequently    -   effecting a change in the header of data packets transmitted to        the communications device.

Paragraph 20. Circuitry for an infrastructure equipment for use in amobile communications network, the mobile communications networkcomprising one or more other infrastructure equipment, theinfrastructure equipment and other infrastructure equipment eachproviding wireless connectivity within at least one cell, and acommunications device configured to communicate wirelessly with theinfrastructure equipment including by the use of a radio bearer, whereinthe infrastructure equipment comprises

-   -   transmitter circuitry configured to transmit signals to the        communications device and to the other infrastructure equipment,    -   receiver circuitry configured to receive signals from the        communications device and from the other infrastructure        equipment, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry    -   to determine that there is a requirement to alter data handling        resources allocated for handling the radio bearer in one or both        of the infrastructure equipment and the communications device,    -   to re-establish, in response to the determination, its radio        link control protocol layer,    -   to transmit a reconfiguration message to the communications        device to effect re-establishment of its radio link control        protocol layer, and subsequently    -   to effect a change in the header of data packets transmitted to        the communications device.

Paragraph 21. A communications device for use in a mobile communicationsnetwork, the mobile communications network comprising one or more otherinfrastructure equipment, the infrastructure equipment and otherinfrastructure equipment each providing wireless connectivity within atleast one cell, wherein the communications device comprises

-   -   transmitter circuitry configured to transmit signals to the        infrastructure equipment,    -   receiver circuitry configured to receive signals from the        infrastructure equipment, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry    -   to communicate wirelessly with at least a first of the        infrastructure equipment including by the use of a radio bearer,    -   to receive a reconfiguration message from the first        infrastructure equipment to effect re-establishment of its radio        link control protocol layer, and subsequently    -   to re-establish its radio link control protocol layer in        response to the reconfiguration message.

Paragraph 22. A method of operating a communications device for use in amobile communications network, the mobile communications networkcomprising one or more other infrastructure equipment, theinfrastructure equipment and other infrastructure equipment eachproviding wireless connectivity within at least one cell, wherein themethod comprises

-   -   communicating wirelessly with at least a first of the        infrastructure equipment including by the use of a radio bearer,    -   receiving a reconfiguration message from the first        infrastructure equipment to effect re-establishment of its radio        link control protocol layer, and subsequently    -   re-establishing its radio link control protocol layer in        response to the reconfiguration message.

Paragraph 23. Circuitry for a communications device for use in a mobilecommunications network, the mobile communications network comprising oneor more other infrastructure equipment, the infrastructure equipment andother infrastructure equipment each providing wireless connectivitywithin at least one cell, wherein the communications device comprises

-   -   transmitter circuitry configured to transmit signals to the        infrastructure equipment,    -   receiver circuitry configured to receive signals from the        infrastructure equipment, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry    -   to communicate wirelessly with at least a first of the        infrastructure equipment including by the use of a radio bearer,    -   to receive a reconfiguration message from the first        infrastructure equipment to effect re-establishment of its radio        link control protocol layer, and subsequently to re-establish        its radio link control protocol layer in response to the        reconfiguration message.

Numerous modifications and variations of the present disclosure arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced otherwise than as specifically described herein.

In so far as embodiments of the disclosure have been described as beingimplemented, at least in part, by software-controlled data processingapparatus, it will be appreciated that a non-transitory machine-readablemedium carrying such software, such as an optical disk, a magnetic disk,semiconductor memory or the like, is also considered to represent anembodiment of the present disclosure.

It will be appreciated that the above description for clarity hasdescribed embodiments with reference to different functional units,circuitry and/or processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits, circuitry and/or processors may be used without detracting fromthe embodiments.

Described embodiments may be implemented in any suitable form includinghardware, software, firmware or any combination of these. Describedembodiments may optionally be implemented at least partly as computersoftware running on one or more data processors and/or digital signalprocessors. The elements and components of any embodiment may bephysically, functionally and logically implemented in any suitable way.Indeed the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units. As such, thedisclosed embodiments may be implemented in a single unit or may bephysically and functionally distributed between different units,circuitry and/or processors.

Although the present disclosure has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Additionally, although a feature may appear to bedescribed in connection with particular embodiments, one skilled in theart would recognize that various features of the described embodimentsmay be combined in any manner suitable to implement the technique.

REFERENCES

-   [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based    radio access”, John Wiley and Sons, 2009

What is claimed is:
 1. A communications device for use in a mobilecommunications network, the mobile communications network comprising oneor more other infrastructure equipment, the infrastructure equipment andother infrastructure equipment each providing wireless connectivitywithin at least one cell, wherein the communications device comprises:transmitter circuitry configured to transmit signals to theinfrastructure equipment; receiver circuitry configured to receivesignals from the infrastructure equipment; and controller circuitryconfigured to control the transmitter circuitry and the receivercircuitry to communicate wirelessly with at least a first of theinfrastructure equipment including by the use of a radio bearer, toreceive a reconfiguration message from the first infrastructureequipment to effect re-establishment of its radio link control protocollayer, and subsequently to re-establish its radio link control protocollayer in response to the reconfiguration message.
 2. A communicationsdevice according to claim 1, wherein the controller circuitry is furtherconfigured to receive data packets from the first infrastructureequipment including a new bit in a header of the data packets.
 3. Acommunications device according to claim 2, wherein the new bit is addedto the header of the data packets for a predetermined time after there-establishment of the radio link control protocol layer of the firstinfrastructure equipment.
 4. A communications device according to claim1, wherein the cells are arranged into a master cell group under controlof the first infrastructure equipment, the first infrastructureequipment being a master infrastructure equipment, and a secondary cellgroup under control of a secondary infrastructure equipment, and thecommunications device is configured to communicate wirelessly with themaster infrastructure equipment and the secondary infrastructureequipment, and wherein the radio bearer is configured for dualconnectivity and receivable at the secondary infrastructure equipmentfor splitting between the secondary infrastructure equipment and themaster infrastructure equipment before delivery to the communicationsdevice.
 5. A communications device according to claim 1, wherein thecells are arranged into a master cell group under control of a masterinfrastructure equipment and a secondary cell group under control of thefirst infrastructure equipment, the first infrastructure equipment beinga secondary infrastructure equipment, and the communications device isconfigured to communicate wirelessly with the master infrastructureequipment and the secondary infrastructure equipment, and wherein theradio bearer is configured for dual connectivity and receivable at thesecondary infrastructure equipment for splitting between the secondaryinfrastructure equipment and the master infrastructure equipment beforedelivery to the communications device.
 6. A communications deviceaccording to claim 1, wherein, subsequent to re-establishing its radiolink control protocol layer, the controller circuitry is configured todiscard one or more data packets with headers that have not been changedby the first infrastructure equipment from a buffer in thecommunications device.
 7. A communications device according to claim 1,wherein, subsequent to re-establishing its radio link control protocollayer, the controller circuitry is configured to control storage ofreceived data packets with headers that have or have not been changed bythe first infrastructure equipment into separate buffers of thecommunications device.
 8. A method of operating a communications devicefor use in a mobile communications network, the mobile communicationsnetwork comprising one or more other infrastructure equipment, theinfrastructure equipment and other infrastructure equipment eachproviding wireless connectivity within at least one cell, wherein themethod comprises: communicating wirelessly with at least a first of theinfrastructure equipment including by the use of a radio bearer,receiving a reconfiguration message from the first infrastructureequipment to effect re-establishment of its radio link control protocollayer, and subsequently re-establishing its radio link control protocollayer in response to the reconfiguration message.
 9. A method accordingto claim 8, further comprising receiving data packets from the firstinfrastructure equipment including a new bit in a header of the datapackets.
 10. A method according to claim 9, wherein the new bit is addedto the header of the data packets for a predetermined time after there-establishment of the radio link control protocol layer of the firstinfrastructure equipment.
 11. A method according to claim 8, wherein thecells are arranged into a master cell group under control of the firstinfrastructure equipment, the first infrastructure equipment being amaster infrastructure equipment, and a secondary cell group undercontrol of a secondary infrastructure equipment, and the communicationsdevice is configured to communicate wirelessly with the masterinfrastructure equipment and the secondary infrastructure equipment, andwherein the radio bearer is configured for dual connectivity andreceivable at the secondary infrastructure equipment for splittingbetween the secondary infrastructure equipment and the masterinfrastructure equipment before delivery to the communications device.12. A method according to claim 8, wherein the cells are arranged into amaster cell group under control of a master infrastructure equipment anda secondary cell group under control of the first infrastructureequipment, the first infrastructure equipment being a secondaryinfrastructure equipment, and the communications device is configured tocommunicate wirelessly with the master infrastructure equipment and thesecondary infrastructure equipment, and wherein the radio bearer isconfigured for dual connectivity and receivable at the secondaryinfrastructure equipment for splitting between the secondaryinfrastructure equipment and the master infrastructure equipment beforedelivery to the communications device.
 13. A method according to claim8, wherein, subsequent to re-establishing its radio link controlprotocol layer, discarding one or more data packets with headers thathave not been changed by the first infrastructure equipment from abuffer in the communications device.
 14. A method according to claim 8,wherein, subsequent to re-establishing its radio link control protocollayer, controlling storage of received data packets with headers thathave or have not been changed by the first infrastructure equipment intoseparate buffers of the communications device.
 15. Circuitry for acommunications device for use in a mobile communications network, themobile communications network comprising one or more otherinfrastructure equipment, the infrastructure equipment and otherinfrastructure equipment each providing wireless connectivity within atleast one cell, wherein the communications device comprises: transmittercircuitry configured to transmit signals to the infrastructureequipment, receiver circuitry configured to receive signals from theinfrastructure equipment, and controller circuitry configured to controlthe transmitter circuitry and the receiver circuitry to communicatewirelessly with at least a first of the infrastructure equipmentincluding by the use of a radio bearer, to receive a reconfigurationmessage from the first infrastructure equipment to effectre-establishment of its radio link control protocol layer, andsubsequently to re-establish its radio link control protocol layer inresponse to the reconfiguration message.
 16. Circuitry according toclaim 15, wherein the controller circuitry is further configured toreceive data packets from the first infrastructure equipment including anew bit in a header of the data packets.
 17. Circuitry according toclaim 16, wherein the new bit is added to the header of the data packetsfor a predetermined time after the re-establishment of the radio linkcontrol protocol layer of the first infrastructure equipment. 18.Circuitry according to claim 15, wherein, subsequent to re-establishingits radio link control protocol layer, the controller circuitry isconfigured to discard one or more data packets with headers that havenot been changed by the first infrastructure equipment from a buffer inthe communications device.
 19. Circuitry according to claim 15, wherein,subsequent to re-establishing its radio link control protocol layer, thecontroller circuitry is configured to control storage of received datapackets with headers that have or have not been changed by the firstinfrastructure equipment into separate buffers of the communicationsdevice.